Fixing device

Abstract

A fixing device configured to fix a toner image on a recording material by heating while conveying the recording material that bears the toner image by a nip portion, the fixing device includes a fixing roller having a rubber layer, a rotating member configured to form a contact portion between the rotating member and the fixing roller, and a pressure member configured to form the nip portion cooperatively with the fixing roller. In the fixing device, heat of the rotating member transfers to the fixing roller from the rotating member via the contact portion, and the contact portion includes a region where the pressure is increased after being decreased on a downstream side further than a center of the contact portion in the rotational direction of the rotating member.

What is claimed is: 
     
       1. A fixing device configured to fix a toner image on a recording material by heating while conveying the recording material that bears the toner image by a nip portion, the fixing device comprising:
 a fixing roller including a rubber layer; 
 a rotating member configured to form a contact portion with the fixing roller; and 
 a pressure member configured to form the nip portion by contacting an outer surface of the fixing roller, 
 wherein the rotating member transfers heat to the fixing roller via the contact portion, 
 wherein a pressure distribution in the contact portion includes a pressure decreasing region, where pressure is increased after being decreased, at a downstream side further than a center of the contact portion in the rotational direction of the rotating member, and 
 wherein a most downstream pressure peak at the downstream side than the pressure decreasing region in the contact portion, is lower than a highest pressure peak at an upstream side than the pressure decreasing region in the contact portion. 
 
     
     
       2. The fixing device according to  claim 1 ,
 wherein the rotating member is a cylindrical film, and 
 wherein the fixing device further comprises a contact portion forming member contacting with an inner surface of the film and configured to form the contact portion with the fixing roller via the film. 
 
     
     
       3. The fixing device according to  claim 2 ,
 wherein the contact portion forming member includes a protruding portion protruding toward the fixing roller on a downstream side further than a center of the contact portion in a rotational direction of the film. 
 
     
     
       4. The fixing device according to  claim 2 ,
 wherein the contact portion forming member includes a heater and a supporting member configured to support the heater. 
 
     
     
       5. The fixing device according to  claim 4 ,
 wherein the protruding portion is formed on the supporting member. 
 
     
     
       6. The fixing device according to  claim 3 ,
 wherein the contact portion forming member includes a heater, and 
 wherein the protruding portion is formed on the heater. 
 
     
     
       7. The fixing device according to  claim 5 ,
 wherein the protruding portion protrudes further than a surface of the heater which makes contact with the film. 
 
     
     
       8. The fixing device according to  claim 2 , further comprising a heater configured to heat an inner surface of the film with radiation heat. 
     
     
       9. A fixing device configured to fix a toner image on a recording material by heating while conveying the recording material that bears the toner image by a nip portion, the fixing device comprising:
 a fixing roller including a rubber layer; 
 a cylindrical film; 
 a contact portion forming member configured to make contact with an inner surface of the film, 
 wherein the contact portion forming member is configured to form a contact portion with the fixing roller via the film; and 
 a pressure member configured to form the nip portion by contacting an outer surface of the fixing roller, 
 wherein heat of the film transfers from the film to the fixing roller via the contact portion, 
 wherein a surface of the contact portion forming member opposite to the inner surface of the film includes, at a downstream side than a center of the contact portion in a rotational direction of the film, a flat surface portion parallel to the recording material conveyed at the nip portion and a protruding portion protruding toward the fixing roller at a downstream side further than the flat surface portion in the rotational direction of the film, and 
 wherein a space is provided between the inner surface of the film and the contact portion forming member at a vicinity of a boundary position between the flat surface portion and the protruding portion. 
 
     
     
       10. The fixing device according to  claim 9 ,
 wherein the contact portion forming member includes a heater and a supporting member configured to support the heater. 
 
     
     
       11. The fixing device according to  claim 10 ,
 wherein the protruding portion is formed on the supporting member. 
 
     
     
       12. The fixing device according to  claim 9 ,
 wherein the contact portion forming member includes a heater, and 
 wherein the protruding portion is formed on the heater. 
 
     
     
       13. The fixing device according to  claim 11 ,
 wherein the protruding portion protrudes further than a surface of the heater which makes contact with the film. 
 
     
     
       14. The fixing device according to  claim 9 , further comprising a heater configured to heat an inner surface of the film with radiation heat.